PLUM, the English name both for certain kinds of tree and also generally for their fruit. The plum tree belongs to the genus Prunus, natural order Rosaceae. Cultivated plums are supposed to have originated from one or other of the species P. domestica (wild plum) or P. insititia (bullace). The young shoots of P. domestica are glabrous, and the fruit oblong; in P. insititia the young shoots are pubescent, and the fruit more or less globose. A third species, the common sloe or blackthorn, P. spinosa, has stout spines; its flowers expand before the leaves; and its fruit is very rough to the taste, in which particulars it differs from the two preceding. These
Culinary Plums.
Early Prolific . . . . e. July Victoria . . . Sept.
Belle de Louvain . . Aug. White Magnum Bonum Sept.
Belgian Purple . m. Aug. Pond's Seedling . . . m. Sept.
Czar e. Aug. Diamond m. Sept.
Pershore . . . . e. Aug. Monarch . . . . e. Sept.
Prince Englebert . e. Aug. Grand Duke . . Oct.
Mitchelsons' . . . . b. Sept. Wyedale e. Oct.
Diseases.—The Plum is subject to several diseases of fungal origin. A widespread disease known as pocket-plums or bladder-plums is due to an ascomycetous fungus, Exoascus pruni, the mycelium of which lives parasitically in the tissues of the host plant, passes into the ovary of the flower and causes the characteristic malformation of the fruit which becomes a deformed, sometimes curved or flattened, wrinkled dry structure, with a hollow occupying the place of the stone; the bladder plums are yellow at first, subsequently dingy red. The reproductive spores are borne in sacs (asci) which form a dense layer on the surface, appearing like a bloom in July; they are scattered by the wind and propagate the disease. The only remedy is to cut off and burn the diseased branches.
Plum-leaf blister is caused by Polystigma rubrum, a pyrenomycetous fungus which forms thick fleshy reddish patches on the leaves.
PLUMBAGO
The reproductive spores are formed in embedded flesh-shaped receptacles (perithecia) and scattered after the leaves have fallen. The
spots are not often so numerous
as to do much harm to the leaves, air but where the disease is serious
diseased leaves should be collected
and burned. Sloes and bird-
cherries should be removed from
the neighbourhood of plum-trees,
as the various disease-producing
insects and fungi live also on these
species. The branches are some-
times attacked by weevils (Rhyn-
cites) and the larvae of various
moths, and saw-flies (chiefly Erio-
campa) feed on the leaves, and out young branches and leaves are sometimes invaded by Aphides. Leaf-feeding beetles and larvae of moths are best got rid of by shaking the branches and collecting the insects. Slug-worms or saw-fly larvae require treatment by washing with, soapsuds, tobacco and lime-water or hellebore solution, and Aphides by syringing from below and removing all surplus young twigs.